SLVUCS1A july   2023  – august 2023 TPS7H2140-SEP

 

  1.   1
  2.   Description
  3.   Features
  4.   4
  5. 1Evaluation Module Overview
    1. 1.1 Introduction
    2. 1.2 Kit Contents
    3. 1.3 Specification
    4. 1.4 Device Information
  6. 2Hardware
    1. 2.1 Connection Descriptions
      1. 2.1.1 Connectors
    2. 2.2 Variable Resistors for CS and CL
      1. 2.2.1 Current Sense Resistor
      2. 2.2.2 Current Limit Resistors
    3. 2.3 Open-Load Detection Pull-Up Resistors
    4. 2.4 Connecting Channels In Parallel
  7. 3Implementation Results
    1. 3.1 Separated Output Results
      1. 3.1.1 Power Up and Power Down
      2. 3.1.2 Enable and Disable
      3. 3.1.3 Current Sensing
      4. 3.1.4 Load Step Effects Across Output Channels
      5. 3.1.5 Overcurrent Protection
    2. 3.2 Modified Configuration Results
      1. 3.2.1 Short-to-GND (Fast-Trip) Overcurrent
  8. 4Hardware Design Files
    1. 4.1 Schematic
    2. 4.2 PCB Layouts
    3. 4.3 Bill of Materials
  9. 5Additional Information
    1.     Trademarks
  10. 6Related Documentation
  11. 7Revision History

2.2.1 Current Sense Resistor

  • For the most accurate and detailed guidance, please refer to the Accurate Current Sense section of the TPS7H2140-SEP data sheet.

High-accuracy current sensing allows better real-time monitoring and more accurate diagnostics without further calibration. High-accuracy current sensing provides real-time output current monitoring. A current mirror is used to source 1/KCS of the load current, and is reflected as VCS = ICS × RCS. KCS is a constant value (300) across temperature and supply voltage. Verify that the CS voltage is in the linear region (0–4 V) when in normal operation.

When in a fault condition, the CS pin works as a diagnostics report pin. When open load/short to VIN happen in on-state, VCS almost equals to zero. When current limit, thermal shutdown/swing, or open load/short to VIN in disabled-state happen, the voltage is clamped at VCS_FAULT. Channel selection for both current and fault reporting is accomplished through the multiplexer digital inputs (SEL and SEH), which can be configured using jumper J8 (SEH) and jumper J9 (SEL).

Equation 1 is the equation for the current-sense resistor, R29.

Equation 1. R(CS)=VCSICS=VCS×K(CS)IOUTx
GUID-20230302-SS0I-5C85-LBRL-SFJDVTVLMCCZ-low.svgFigure 2-1 Current-Sense Output-Voltage Curve

Take the following points into consideration when calculating RCS.

  • Verify that VCS is within the current-sense linear region (VCS_LINEAR, IOUTx_LINEAR) across the full range of the load current. Check RCS with Equation 2.
    Equation 2. RCS=VCSICS≤VCS_LINEAR(MAX) × KCS  IOUTx(MAX)
  • In fault mode, verify that ICS is within the source capacity of the CS pin (ICS_FAULT). Check RCS with Equation 3.
    Equation 3. RCS=VCSICS≥VCS_FAULT(MAX)  ICS_FAULT(MIN)